Labile nutrient metals: Free agents in redox systems

Redox-active, nutrient trace metals, iron, copper, cobalt, manganese, and molybdenum, are involved in a wide array of processes in human physiology. The roles of these redox metals in biological systems have been studied and reviewed widely, usually with heavy emphasis on their roles as protein cofactors. However, labile pools of redox metal ions influence these systems as well. In this short review, the chemistries and biological contexts of labile nutrient redox metals are summarized. Next, three forms of influence on human systems common among labile redox metal ions are explored: 1) catalysis of redox reactions by free metal ions, 2) influences of redox metal ions on abundances of other metal species and 3) redox metal ion interactions with low-molecular weight metabolites. Finally, a brief sampling of modern techniques to study redox metal ions is explored. The activities of labile pools of redox metal ions generate a network of metals interacting with other facets of biological systems, and modern metallomics methods and systems-based analytical approaches finally enable high-dimensional study of these interactions to improve our understandings of human health.